Examples

Description

Define a fix that stores attributes for each atom in the group at the
time the fix is defined. If N is 0, then the values are never
updated, so this is a way of archiving an atom attribute at a given
time for future use in a calculation or output. See the discussion of
output commands that take fixes as
inputs.

If N is not zero, then the attributes will be updated every N
steps.

Note

Actually, only atom attributes specified by keywords like xu
or vy or radius are initially stored immediately at the point in
your input script when the fix is defined. Attributes specified by a
compute, fix, or variable are not initially stored until the first run
following the fix definition begins. This is because calculating
those attributes may require quantities that are not defined in
between runs.

The list of possible attributes is the same as that used by the dump custom command, which describes their meaning.

If the com keyword is set to yes then the xu, yu, and zu
inputs store the position of each atom relative to the center-of-mass
of the group of atoms, instead of storing the absolute position.

The requested values are stored in a per-atom vector or array as
discussed below. Zeroes are stored for atoms not in the specified
group.

Restart, fix_modify, output, run start/stop, minimize info:

This fix writes the per-atom values it stores to binary restart files, so that the values can be restored when a
simulation is restarted. See the read_restart
command for info on how to re-specify a fix in an input script that
reads a restart file, so that the operation of the fix continues in an
uninterrupted fashion.

If a single input is specified, this fix produces a per-atom vector.
If multiple inputs are specified, a per-atom array is produced where
the number of columns for each atom is the number of inputs. These
can be accessed by various output commands. The per-atom values be
accessed on any timestep.

No parameter of this fix can be used with the start/stop keywords of
the run command. This fix is not invoked during energy minimization.